This invention relates to ionic resins, and more particularly, to resinous reaction products of a polymer of an amine and an epihalohydrin and to their use in the manufacture of paper having good wet strength properties and good dry strength properties.
The use of the reaction products of a polymer of an amine and an epihalohydrin to improve the wet strength and dry strength of cellulosic substrates is well known to the art. Indeed, this class of materials is widely used in the manufacture of paper products and millions of pounds of these resinous products are consumed each year to satisfy the needs of the paper industry.
A number of processes and compositions are taught in the prior art for the preparation and use of such resinous reaction products. As an example, U.S. Pat. 2,595,935 discloses paper products of improved wet strength containing the reaction product of polyalkanepolyamines and bifunctional or polyfunctional halohydrins, such as epichlorohydrin. German Pat. No. 955,835 discloses a process for water-proofing paper by adding to the pulp basic products free from reactive halogen or epoxy groups. These products are obtained by condensing polyamines with cross-linking compounds, such as epichlorohydrin or dichloroethane. Such products also increase the wet strength of paper. U.S. Pat. 2,834,675 discloses resinous compositions of dihaloalkanes and polyalkylenepolyamines which may be added to paper pulp to improve the wet strength. U.S. Pat. No. 3,700,623 discloses the reaction products of an epihalohydrin and a polymer of a diallylamine useful as wet strength agents, and additionally, give superior dry strength properties to paper. U.S. Pat. No. 3,855,158 discloses cationic resinous compositions comprising the reaction product of an adduct of certain dihaloalkanes and polyalkylenepolyamines and certain epihalohydrins to be added to cellulosic substrates to increase the wet strength of the product.
Although the teachings of the prior art provide products that give paper satisfactory wet strength and dry strength properties, it has now been found that fast curing, ionic, thermosetting resins can be prepared by the process of the present invention, and that the resins so produced provide all of the advantages of the prior art resins and, in addition, provide advantages not achieved by products disclosed in the prior art. For example, the resins of the present invention are more efficient since less resin is required to provide equivalent wet strength and dry strength properties to cellulosic substrates, such as paper, paperboard, and the like.
In addition, the prior art discloses that less than 80% of the epihalohydrin will react with a polyamine hydrohalide salt or with a polyamine containing high levels of halide ion, such as by neutralization of the hydrohalide with a base. Although Applicants do not wish to be bound by any particular theory, it is believed that the halide ion reacts with some of the epihalohydrin, making it unreactive and/or less reactive with the polyamine. In the present invention, a substantial amount (i.e., greater than 50%) of the halide ion is removed from the polyamine before condensation with an epihalohydrin, with the result that more of the epihalohydrin is available to react with the polyamine. The resulting resinous reaction product provides superior wet strength and dry strength when applied to cellulosic substrates.